bouldersmith: "Usually the the barrel, lock and often the buttstock were saved. An action, often Jones under lever style was fabricated with the fore thought of utilizing the existing parts. Labor was cheap back then. A very small "patch" was silver soldered in place to seal what was the touch hole and to maintain a decent length barrel. Cool stuff for sure. One thing I have noticed it that many of the early conversions have very thin breech balls and often have a very sharp corner at the junction of the water table and the standing breech."
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Similar conversions were often done, pinfire to center fire, guns/rifles, most of them from mid 1860s. They too had thin breech balls and sharp corner, junction of water table and standing breech; where later experience taught that action cracking occurred there, so sharp corner was soon replaced by rounded corner, as we now see so common today.